/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package pku.lbs.web.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import net.sf.json.JSONObject;

/**
 *
 * @author yongchao
 */
public abstract class BaseServlet extends HttpServlet {

    protected String jsonInvalidRequest() {
        JSONObject json = new JSONObject();
        json.put("RETURN", false);
        json.put("MESSAGE", "INVALID REQUEST");
        return json.toString();
    }

    abstract protected String processAction(String action, HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException;

    /**
     * Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
     * @param request servlet request
     * @param response servlet response
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        String jsonStr = null;

        // GET ACTION STRING, RETURN IF EMPTY
        String action = (String) request.getParameter("action");
        if (action == null || action.length() == 0) {
            jsonStr = jsonInvalidRequest();
        } else {
            action = action.toUpperCase();
            // CALL ACTIONS DEFINED IN CHILD CLASS, GET RETURN STRING IN JSON FORMAT
            jsonStr = processAction(action, request, response);
        }

        // SEND USER DATA (JSON STRING) BACK TO JAVASCRIPT
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        try {
            out.println(jsonStr);
        } finally {
            out.close();
        }
    }
    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /**
     * Handles the HTTP <code>GET</code> method.
     * @param request servlet request
     * @param response servlet response
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Handles the HTTP <code>POST</code> method.
     * @param request servlet request
     * @param response servlet response
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Returns a short description of the servlet.
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>
}
